fn f(i:i32)->Result<i32,bool>{
    if i>=0{
        Ok(i)
    }
    else{
        Err(false)
    }
}
fn g(i:i32)->Result<i32,bool>{
    let t=f(i)?;
    Ok(t)
}
pub fn main() {
    let r=f(1);
    match r{
        Ok(i)=>{
            println!("ok:{}",i);
        },
        Err(err)=>{
            println!("error:{}",err);
        }
    }
}
